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Re: Alternative to 303 response: Description-ID: header

From: Ian Davis <lists@iandavis.com>
Date: Wed, 05 Dec 2007 15:55:14 +0000
To: Tim Berners-Lee <timbl@w3.org>
Cc: "Sean B. Palmer" <sean@miscoranda.com>, David Booth <dbooth@hp.com>, www-tag@w3.org
Message-Id: <1196870114.15636.18.camel@iand-laptop>

On Wed, 2007-12-05 at 10:31 -0500, Tim Berners-Lee wrote:
> Ian,
> Your blog says, in http://iandavis.com/blog/2007/12/303-asymmetry
> 'Suppose I have a resource “R” with URI http://example.org/R. If it is  
> an “Information Resource” then I can arrange things so that a GET  
> request for its text/html representation responds with a 200 and the  
> HTML in the body of the response. I could also arrange for a request  
> for its application/rdf+xml representation to respond with a 303  
> status and the URI of another information resource “RDESC” (e.g. http://example.org/RDESC) 
> . In this example the 303 response meand that “R” cannot be  
> represented as RDF, but there’s an alternative RDF document that is a  
> description of R."
> There is a major problem with this, though.   Content negotiation is  
> just for different encodings of the

> On 2007-12 -04, at 20:56, Ian Davis wrote:
> >
> > On Tue, 2007-12-04 at 19:53 -0500, Tim Berners-Lee wrote:
> >>
> >> I did wonder about the following:  in the case when the URI is not of
> >> document, when currently we use 303,
> >> then the  server can return a document *about* it with  an extra
> >> header to explain to the browser
> >> that it is actually giving you a description of it not the content of
> >> it.  (Pick a header name)
> >
> >
> > Strange synchronicity... I posted the same idea a few minutes ago to  
> > my
> > blog:
> >
> > http://iandavis.com/blog/2007/12/303-asymmetry
> >
> > I called my header "resource-description"
> >
> > Ian
>  SAME document.
> You can content negotiate between PNG and JPG of the SAME picture.
> Between text/plain and text/html of the SAME document.
> Between RDF/xml and N3 of the SAME data.
> You cannot use conneg to return a completely different document, eg  
> not A but  metadata bout A.
> A and A' must carry exactly the same information, module an  
> 'acceptable' degree of degradation.
OK. But in my blog post I'm not suggesting returning both RDF and HTML
via conneg. I'm saying that you could return HTML for the information
resource and a 303 when asked for an RDF representation, meaning the
server doesn't have one but see this other document instead.

> When people conneg between HTML and RDF, the HTML is generated from  
> the RDF. Else it is  a bug.

I think there's still a clash of fragment identifier semantics even in
this case... but that's a different issue.

> You say, "How can I allow the user to obtain a description of RDESC?  
> The representation I send back is the content of RDESC, not its  
> description. I can’t use the media type to distinguish the type of  
> request any more."
> Sorry, you never could.
> The resource-description header you suggest seems very similar to teh  
> HHP link header, Link: foo.rdf; rel=meta
> (se http://esw.w3.org/topic/LinkHeader)

Yes. We better hurry up and get the link header through the ietf - there
are more and more uses for it every day :)

> Tim

Received on Wednesday, 5 December 2007 15:57:28 UTC

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